Paramyotonia Congenita with Persistent Distal and Facial Muscle Weakness: A Case Report with Literature Review

Taminato, Tomoya; Mori‐Yoshimura, Madoka; Miki, Jun; Sasaki, Ryo; Sato, Noriko; Oya, Yasushi; Nishino, Ichizo; Takahashi, Yūji

doi:10.3233/jnd-190440

Cited by 5 publications

(10 citation statements)

References 57 publications

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“…For the majority of patients, the pattern of weakness or extra‐muscular manifestations distinguish these disorders (see the Differential Diagnosis section). That said, there are isolated families described with SCN4A mutations and either distal weakness, or more profound proximal weakness 61,62 . A proportion of patients with NDM have pain as well.…”

Section: General Clinical Presentationmentioning

confidence: 99%

Guidelines on clinical presentation and management of nondystrophic myotonias

et al. 2020

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The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present.

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Section: General Clinical Presentationmentioning

confidence: 99%

Guidelines on clinical presentation and management of nondystrophic myotonias

et al. 2020

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“…Again, this argues for a continuum of these disorders and suggests the importance of disease-modifying genes. As more mutations are identified, many variable phenotypes are emerging, such as myotonia with normokalemic/hypokalemic PP, PP associated with myotonia instead of paradoxical myotonia, or the presence of myopathic traits [ 13 , 14 , 15 , 16 , 17 , 18 ].…”

Section: Skeletal Muscle Sodium Channelopathiesmentioning

confidence: 99%

Ion Channel Gene Mutations Causing Skeletal Muscle Disorders: Pathomechanisms and Opportunities for Therapy

Maggi

Bonanno

Altamura

et al. 2021

Cells

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Skeletal muscle ion channelopathies (SMICs) are a large heterogeneous group of rare genetic disorders caused by mutations in genes encoding ion channel subunits in the skeletal muscle mainly characterized by myotonia or periodic paralysis, potentially resulting in long-term disabilities. However, with the development of new molecular technologies, new genes and new phenotypes, including progressive myopathies, have been recently discovered, markedly increasing the complexity in the field. In this regard, new advances in SMICs show a less conventional role of ion channels in muscle cell division, proliferation, differentiation, and survival. Hence, SMICs represent an expanding and exciting field. Here, we review current knowledge of SMICs, with a description of their clinical phenotypes, cellular and molecular pathomechanisms, and available treatments.

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“…(n = 8, 1 kindred) [77] positive to ACZ (500 mg) (n = 1), paramyotonia improved but not persistent weakness NR to ACZ (250 mg)…”

Section: Randomized Clinical Trials (Class Of Evidence I)mentioning

confidence: 99%

“…Myopathy is generally not a predominant trait of gain-of-function muscle ion channelopathies, with only some rare exceptions [60,77,84,201,202]. Non-dystrophic myotonias can be associated with a Herculean appearance, due to continuous muscle contractions.…”

Section: Congenital Myopathies Related To Scn4a/cacna1smentioning

confidence: 99%

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Targeted Therapies for Skeletal Muscle Ion Channelopathies: Systematic Review and Steps Towards Precision Medicine

Desaphy

Altamura

Vicart

et al. 2021

JND

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Background: Skeletal muscle ion channelopathies include non-dystrophic myotonias (NDM), periodic paralyses (PP), congenital myasthenic syndrome, and recently identified congenital myopathies. The treatment of these diseases is mainly symptomatic, aimed at reducing muscle excitability in NDM or modifying triggers of attacks in PP. Objective: This systematic review collected the evidences regarding effects of pharmacological treatment on muscle ion channelopathies, focusing on the possible link between treatments and genetic background. Methods: We searched databases for randomized clinical trials (RCT) and other human studies reporting pharmacological treatments. Preclinical studies were considered to gain further information regarding mutation-dependent drug effects. All steps were performed by two independent investigators, while two others critically reviewed the entire process. Results: For NMD, RCT showed therapeutic benefits of mexiletine and lamotrigine, while other human studies suggest some efficacy of various sodium channel blockers and of the carbonic anhydrase inhibitor (CAI) acetazolamide. Preclinical studies suggest that mutations may alter sensitivity of the channel to sodium channel blockers in vitro, which has been translated to humans in some cases. For hyperkalemic and hypokalemic PP, RCT showed efficacy of the CAI dichlorphenamide in preventing paralysis. However, hypokalemic PP patients carrying sodium channel mutations may have fewer benefits from DCP compared to those carrying calcium channel mutations. Few data are available for treatment of congenital myopathies. Conclusions: These studies provided limited information about the response to treatments of individual mutations or groups of mutations. A major effort is needed to perform human studies for designing a mutation-driven precision medicine in muscle ion channelopathies.

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Paramyotonia Congenita with Persistent Distal and Facial Muscle Weakness: A Case Report with Literature Review

Cited by 5 publications

References 57 publications

Guidelines on clinical presentation and management of nondystrophic myotonias

Guidelines on clinical presentation and management of nondystrophic myotonias

Ion Channel Gene Mutations Causing Skeletal Muscle Disorders: Pathomechanisms and Opportunities for Therapy

Targeted Therapies for Skeletal Muscle Ion Channelopathies: Systematic Review and Steps Towards Precision Medicine

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